Having once worn a dress made entirely of raw meat, the pop singer Lady Gaga is famous — or notorious, depending upon how you feel about food as frockery — for her extravagant, often risqué, outfits. ■

But when 26-year-old Stefani Joanne Angelina Germanotta hit the concert scene this year, watchers went wild for different reason: Her skimpy costumes revealed that there was more of her to reveal.

The singer had added about 30 pounds to her 5-foot-1, formerly 100-pound frame, spawning a storm of magazine stories, blog posts and snarky jokes. It was a Gaga brouhaha.

Americans worry a lot about body weight, theirs and everybody else’s. Gaga’s Body Mass Index still falls within the “normal” range, but in a July Gallup poll, 81 percent of Americans said obesity was an “extremely serious” or “very serious” social problem. Smoking came in a distant second at 67 percent.

“For the first time,” observed writer Daniel Engber in Slate, “respondents have shown that they’re more worried about jiggly thighs than blackened lungs.”

To be sure, there are a lot more jiggly thighs out there than blackened lungs, not to mention bouncing bellies and wobbly arms. More than two-thirds of American adults (and one-third of their children) are overweight or obese. More than half of our pet dogs and cats are, too.

The causes and effects of obesity thread through the fabric of America, a tangle of confusions, contradictions and controversies. Billions of dollars are spent to persuade us to eat and eat often. Food is continuously reinvented so that it is easier to consume — and harder to resist. For a fattened nation, the ramifications spill out in ways far more troubling than Lady Gaga’s midriff.

Eat your vegetables

Americans eat one-third more processed food than fresh; more packaged food per person than just about anybody else on Earth. This convenient fact contains an inconvenient truth: The more a food is processed, the less it tends to resemble actual food.

Ten ounces of real strawberries, for example, has 90 calories, 5 grams of fiber, abundant vitamins and minerals and myriad phytochemicals believed to promote good health. One ounce of Betty Crocker’s Strawberry Splash Fruit Gushers also contains 90 calories, but zero fiber and almost no measurable nutrients. No actual strawberries, either.

Eating right — and smart — is hard to do. It’s a big part of why so many Americans are so fat. Many things make eating right difficult, even for the well-intentioned. Two cases in point:

1. Unavoidable, ubiquitous advertising. The Journal of Public Health Policy estimates the food industry spends as much as $10 billion a year on advertising, more than the Gross National Product of 61 different countries. Almost $2 billion is spent targeting children. The average child sees roughly 5,500 food commercials on TV every year — about 15 per day.

How many times a day can mom counter by saying, “Carrots are good for you.”

2. Confounding research. Food science is complicated and often misleading, according to Dr. David Ludwig, a Harvard University professor of pediatrics and nutrition. In 2007, Ludwig and colleagues analyzed 206 original scientific research papers and articles published between 1999 and 2003 that examined the health effects of soft drinks, juices and milks.

The majority of the studies were funded, at least in part, by the food and drink industry, though many studies did not explicitly say so. The researchers found a strong association between the type of funding and the conclusions drawn: Studies funded exclusively by industry were four to eight times more likely to have conclusions favorable to the financial interests of the sponsoring company than articles not funded by food or drink companies.

“If a study is funded by the industry,” Ludwig told US News & World Report, “it may be closer to advertising than science.”

Overcooked

Everything around us encourages overconsumption. “More food, more often, in more places than we need,” said Marion Nestle, a professor of nutrition, food studies and public health at New York University.

Americans have access to more calories per day per capita — 3,800 — than anyone else in the world. Roughly one-third of these calories are lost to things like spoilage and plate waste, but each of us still manages to gobble down an average of 2,700 calories per day, about 530 more than we did in 1970.

This easy abundance is a relatively new phenomenon, according to Margaret Schoeninger, a professor of anthropology at UC San Diego who studies the evolution of the human diet. “Even a generation or so ago, we didn’t eat like we do now, walking, driving, at any time,” she said.

“Humans are omnivores so we’ll eat whatever we can get, but we’re not really set up biologically to consume food all of the time. In that, we’re not alone. Dogs are omnivores too, but if you let them eat whenever they want, they get obese as well.”

One reason we eat so much involves how we cook food. As late as the 1960s, the vast majority of meals were prepared and eaten at home. Now, it’s less than half. In 1965, a married woman who didn’t work spent, on average, more than two hours per day cooking and cleaning up after meals.

Then a sort of revolution in the mass food preparation occurred, according to Harvard University economists David M. Cutler, Edward L. Glaeser and Jesse M. Shapiro. Technological innovations like vacuum packing, artificial flavors and microwave ovens dramatically cut the time and effort needed to prepare meals. The ability to cheaply manufacture food for the masses meant greater quantity and variety.

The proof is in the potato. “Before World War II, Americans ate massive amounts of potatoes, largely baked, boiled or mashed,” the economists wrote in their 2003 study. “French fries were rare, both at home and in restaurants, because the preparation requires significant peeling, cutting and cooking.”

But machines were invented that could peel, cut and cook potatoes almost automatically at central locations, then freeze and ship them to any place in the country where they could be quickly reheated in deep fryers, ovens or microwaves.

“Today, the French fry is the dominant form of potato and America’s favorite vegetable,” the economists wrote. Total potato consumption has risen more than 30 percent since 1977. So has the related national calorie count: A medium serving of fast-food french fries these days packs between 390 and 450 calories, roughly half from fat. The medium, unadorned baked potato of yore contains a comparatively paltry 160.

Think before you drink

Food makers and purveyors aren’t particularly interested in changing (i.e., reducing) American consumption patterns. It’s not in their financial interest. That leaves government policymakers and regulators to act as, well, mom.

Everyone knows that’s a hard and thankless job.

Take New York City’s recent ban on the sale of large, sugar-sweetened drinks such as sodas, “sports” beverages, sweetened teas and coffees, and fruit and energy drinks. The ban limits maximum beverage size to 16 ounces.

That sound you hear is Americans everywhere gulping, big time. The average American consumes 222 calories a day in the form of soda or other sugary beverages. Male teens drink an average of 868 cans of soda a year; more than half of all 8-year-olds drink at least one can a day. The consumption of sugary drinks over the last 40 years has paralleled the obesity rate, though the American Beverage Association dismisses the correlation, noting that soda consumption has declined in recent years (though other sugary drinks have not).

New York’s beverage ban aroused great ire and controversy. In defending it, Mayor Michael Bloomberg said, “All we’re doing here is educating. It forces you to see the difference.”

It may not make a difference. The ban doesn’t necessarily ban anything.

“One hundred and fifty years of research in food economics tells us that people get what they want,” Brian Wansink, a professor of marketing and director of the Food and Brand Lab at Cornell University told The Wall Street Journal. “Someone who buys a 32-ounce soft drink wants a 32-ounce soft drink. He or she will go to a place that offers fountain refills, or buy two.”

But many nutrition and health activists laud the ban as a step in the right direction. They point to the connection — correlation to causal — between excessive body weight and scores of diseases and health conditions.

“Some of the most important public health measures — those that have saved millions of lives — were accomplished through government intervention: chlorinated water, vaccination, seat belts, helmets and anti-smoking measures,” Nestle said.

“Taxpayers are responsible for the health care costs of self-interested individual behavior, so taxpayers have a vested interest in keeping people healthy.”

Food for naught

The problem with fat is that it doesn’t spread evenly — on people or in nations.

Wansink says New York’s soda ban will affect poor people much more than rich, noting that soft drinks are purchased by one-third of the city’s poorest 2 million, but by just one-sixth of the city’s richest top million people.

Associations between weight and socioeconomic status are controversial. In economically developed countries, conventional wisdom holds that obesity is lower among the wealthy because they can afford more nutritious food, they feel greater social pressure to remain slim and they have better access and resources for staying fit.

Among the most widely cited reasons for why some Americans are obese is because they live in poorer neighborhoods dubbed “food deserts,” places where cheap fast-food joints and convenience stores outnumber full-service supermarkets. These are neighborhoods where it’s presumed to be easier or cheaper to eat badly than well.

“We all grew up in communities with grandmothers who cooked two, three vegetables that you had to eat,” said first lady Michelle Obama last year at a Chicago conference on food deserts. “There were no ifs, ands or buts about it. But that’s because many of our grandparents, they had community gardens; there was the vegetable man that came around. There were many other resources that allowed them to have access. So it’s not that people don’t know or don’t want to do the right thing; they just have to have access to the foods that they know will make their families healthier.”

Food deserts have been broadly linked to the obesity problem — and they may be — but there is some evidence to argue otherwise. A pair of new studies published this year, for example, found that poor, urban neighborhoods actually have lots of everything: fast-food joints, convenience stores, supermarkets and full-service restaurants.

“You can get basically any type of food,” Roland Sturm, lead author of one of the studies, told The New York Times. “Maybe we should call it a food swamp.”

Swamp or not, without real changes on all scales, obesity may be our just dessert.

Scott LaFee, a former science writer for The San Diego Union-Tribune, is a senior public information officer for health sciences research at the University of California San Diego. Email: health@utsandiego.com